The discovery of X-rays by Rontgen in 1895, and of radioactivity by Becquerel in 1896, was followed by an early appreciation of both the damaging and therapeutic effects of ionizing and ultraviolet radiation (including genetic effects, for which Muller later received the Nobel Prize). From this emerged radiation research, a multidisciplinary field embracing physics, chemistry, biology, and medicine, all of which are used to the benefit of man. The Radiation Research Society was formed in the USA in 1952 and was followed soon after by the formation of socieities in Great Britain, the Netherlands, Sweden, Poland, the European Society (including Germany, France, Italy, and others), Japan and Israel. These societies now form the International Association for Radiation Research (IARR), a component of the International Union of the Biological Sciences. The 1st International Congress of Radiation Research was held in Burlington, Vermont in 1958 and since then, at four-year intervals, international congresses sponsored by IARR have been held in England, Italy, France, and the United States. The VIth Congress is to be held in Tokyo, Japan from 13-19 May 1979. The multidisciplinary nature of the subject renders these international meetings especially valuable. Physicists, chemists, biologists, and physicians interested in environmental hazards in general (i.e., including hazards from chemical pollutants), as well as cancer research and cancer therapy in general, will meet to discuss their progress. It is appropriate that a substantial contingent of attendees be from North America, and principally from the United States (and territories related to it), in view of the leading role of American scientists in the development of atomic energy, new technologies for energy production (e.g., from coal and from the sun), and various aspects of research in the causes and treatment of cancer.